song (n.)

Old English sang "voice, song, art of singing; metrical composition adapted for singing, psalm, poem," from Proto-Germanic *songwho- (source also of Old Norse söngr, Norwegian song, Swedish sång, Old Saxon, Danish, Old Frisian, Old High German, German sang, Middle Dutch sanc, Dutch zang, Gothic saggws), from PIE *songwh-o- "singing, song," from *sengwh- "to sing, make an incantation" (see sing (v.)).

Phrase for a song "for a trifle, for little or nothing" is from "All's Well" III.ii.9 (the identical image, por du son, is in Old French. With a song in (one's) heart "feeling joy" is first attested 1930 in Lorenz Hart's lyric. Song and dance as a form of vaudeville act is attested from 1872; figurative sense of "rigmarole" is from 1895.

Definitions of song
song (n.)
a short musical composition with words;
a successful musical must have at least three good songs
Synonyms: vocal
song (n.)
a distinctive or characteristic sound;
the song of bullets was in the air
the song of the wind
the wheels sang their song as the train rocketed ahead
song (n.)
the act of singing;
with a shout and a song they marched up to the gates
Synonyms: strain
song (n.)
the characteristic sound produced by a bird;
a bird will not learn its song unless it hears it at an early age
Synonyms: birdcall / call / birdsong
song (n.)
a very small sum;
he bought it for a song
Song (n.)
the imperial dynasty of China from 960 to 1279; noted for art and literature and philosophy;
Synonyms: Sung / Sung dynasty / Song dynasty